Meridional circulation dynamics from 3D MHD global simulations of solar convection

TL;DR

This study uses 3D global MHD simulations to analyze solar meridional circulation, revealing its complex dynamics, potential equatorward flow at the convection zone base, and interactions with magnetic fields, which impact observational and modeling approaches.

Contribution

It provides new insights into the dynamical behavior of solar meridional circulation from simulations and compares them with observations, highlighting the importance of magnetic interactions.

Findings

Equatorward flow likely exists at the base of the convection zone.

Meridional circulation morphology changes with the magnetic cycle.

Magnetic fields significantly influence plasma flow dynamics.

Abstract

The form of the solar meridional circulation is a very important ingredient for mean field flux transport dynamo models. Yet a shroud of mystery still surrounds this large-scale flow, given that its measurement using current helioseismic techniques is challenging. In this work we use results from 3D global simulations of solar convection to infer the dynamical behavior of the established meridional circulation. We make a direct comparison between the meridional circulation that arises in these simulations and the latest observations. Based on our results we argue that there should be an equatorward flow at the base of the convection zone at mid latitudes, below the current maximum depth helioseismic measures can probe (0.75 R). We also provide physical arguments to justify this behaviour. The simulations indicate that the meridional circulation undergoes substantial changes in morphology as the magnetic cycle unfolds. We close by discussing the importance of these dynamical changes for current methods of observation that involve long averaging periods of helioseismic data. Also noteworthy is the fact that these topological changes indicate a rich interaction between magnetic fields and plasma flows, which challenges the ubiquitous kinematic approach used in the vast majority of mean field dynamo simulations.